Knife sharpening machine



Aug. 22, 1950 G. M. CALVERT KNIFE SHARPENING MACHINE 2 Sheets-Sheet 1 Filed March 22, 1947 INVENTOR.

GLEN M. CALVERT MTTORNEY Patented Aug. 22, 1950 UNITED STATES PATENT OFFICE 20 Claims.

This invention relates to knife sharpening machines, and particularly machines in which abrasive or other cutting elements are reciprocated against opposite faces of a blade.

An object of the invention is to adapt a pair of carriages for abrasive or cutting elements to reciprocate at opposite sides of a blade to be sharpened, transversely to the blade length and in guides converging in conformity to the lateral faces of the blade so that the blade may be In these views, the reference characters I and 2 designate a pair of side walls of a casin having end walls 3 and 4. Rigidly secured to the end wall 3, as by screws 5, is a guide 6 for a uniformly sharpened throughout its length by gradually shifting it lengthwise, while engaged by said abrasive elements.

Another object is to provide for continuously reciprocating said carriages in their guides, so

that their strokes are relatively reverse in direction.

Another object is to adapt the abrasive elements to lap each other as they reciprocate.

Another object is to provide positioning and guiding means for a blade between said carr1ages.

Another object is to adapt the blade positioning and guiding means to float to and from the carriages to position a blade for proper engagement by the abrasive elements and to equalize the abrasive pressure on lateral faces of the blade.

Another object is to provide for resiliently grippin the blade within said positioning and guiding means.

Another object is to provide for adjusting one of said carriage guides to and from the other to compensate for wear of the abrasive elements.

Another object is to resiliently urge one of said carriage guides toward the other and to regulate the urgin force, thus predetermining pressure of abrasive elements against the blade.

These and various other objects are attained by the construction hereinafter described and illustrated in the accompanying drawings, wherein:

reciprocating carriage I. Confronting the guide 6 but spaced therefrom, is a similar guide 8, wherein reciprocates a carriage 9 similar to the carriage l. Each guide 6 and 8 has undercut rails l6 along opposite margins of the guide and each carriage has a pair of flanges l l slidably held by the rails of the corresponding guide. The rails of the two guides are downwardly convergent at a predetermined angle of twenty degrees, this bein the usual and most efiective angle at which the lateral faces of blades converge to form cutting edges. The carriage 1 rigidly and marginally carries a pair of spaced abrasive elements l2 elongated in the direction of reciprocation of said carriage, such elements being clamped in place by plates l3 to which pressure is applied by screws 54. Between its margins carrying the abrasive elements, the carriage 1 is channeled from end to end in its direction of reciprocation, as indicated at 15. The carriage 9 similarly mounts a similar pair of abrasive elements Iii, having a lesser spacing, however, than the elements l2, and hence being adapted to reciprocate between and in close proximity to the elements l2.

The guide 8 is slidable to and from the guide 6, the wall I having a pair of horizontal ribs I! received in channels 18 of the guide 8 to assure a straight line travel of said sliding guide. Connected to the guide 8 for accurately adjusting its sliding travel, is a screw l9 engaging a'threaded opening in the end wall 4, and having an actuating knob 2i! fixed on its outer end. For indicating fractions of a revolution of said screw, it carries a collar 20a, marginally having suitably spaced radial markings coacting with an index line 20b on'the wall 4. Thi col- Fig. l is a perspective view of the knife sharplar is retained in a fixed proximity to the wall 4, while allowing travel of the screw through the collar, by grooving the screw from end to end, as indicated at 2| and radially setting into the collar a screw 22 having its inner end slip-fitted in said groove, a keeper 23 being secured to the wall 4 by screws 24 to receive the lower portion of the collar. It is desirable, in sharpening a knife or other blade to impose a regulable pressure thereon through the described abrasive elements. For this'purpose the screw I9 is made tubular and houses a coiled spring 25 between a plunger 26 projecting from the inner end of the screw and a small cylindrical a abutment 2?, adjustable to vary compression of the spring. The adjusting means is a screw 28, freely bearing on the abutment 2? and set into a feed nut 29 having the nature of a plug fixedly mounted in the outer end of the screw 19. The plunger 26 has an end enlarged within the inner end of the screw l9 and engageable with an interior shoulder in such end to prevent escape of the plunger. The projecting end portion of the plunger is set into a bore 39 in the guide 8 and is annularly grooved to receive a screw 3i laterally set into said guide.

For reciprocating the two carriages, connecting rods 32 are extended therefrom to a pair of intermeshed gears 33 journaled adjacent to the wall i on shafts 34 and 35. One of said shafts, as 34, is adapted to be continuously driven from any suitable source of power when the machine is in use. The connecting rods are so attached to the gears as to move the carriages always in reverse directions. This avoids the clearance problem that would result from concurrently bringing the carriages to positions in which their paths lap each other, and also permits the abrasive forces acting against opposite faces of a blade to counteract each other.

Between the two carriage guides is mounted a blade-positioning and guiding member, which will now be described. This member comprises a frame 35 formed by a pair of plates respectively parallel to and engaging the respective walls i and 2, and top and bottom plates. Said frame has one of its side plates horizontally grooved at 31 to receive the ribs 11, whereby the frame may float to and from the guides and 8, while being restrained from any tilting. A slot 38 extends across the top of such frame and sufficiently down the sides thereof to admit a blade to be sharpened, such as shown at 39. Within the frame 36, a pair of blade-engaging jaws 4B of inverted U- shape are mounted at opposite sides of the slot 38, with their adjoined margins slightly obstructing the slot. Each of these jaws is supported by a pair of screws 4! extending through slots 4 la in the top of the frame 36 and headed above such frame, and a wire spring d2, anchored midway of its length by a screw 33, bears terminally on each pair of screws M to urge the jaws 40 toward each other. Midway between its side plates, the frame 36 carries another pair of blade-clamping jaws 44, these being vertically elongated and urged toward each other by bowed springs 45 interposed between said jaws and a pair of vertically elongated metal straps 46 having upper end portions oppositely bent and anchored to and beneath the top of the frame 36 by said screws 43. A block 47 is secured to the lower end of one .-o f the straps 46 and is formed with a downwardly aqrtending narrow groove 48 to receive the edge gpbrtion of a blade and establish a lower limiting -.flfion of the blade while avoiding contact with putting edge. Similar blocks 49 are carried 'geipectively by the respective side walls of the frame 38 within enlarged lower portions of the slot 38. The walls I and 2 have blade-receiving slots 50 extending downwardly from their top margins, midway between the end walls 3 and t, such slots being wide enough to accommodate a blade within a considerable range of floating horizontal travel of the described blade-positioning and guiding member.

In use of the described machine, the shaft 34 is driven at a moderate speed by an electric motor (not shown) or in any other suitable manner, whereby the carriages 1 and 9 reciprocate intheir convergent paths established by the guides 6 and 8. A blade to be sharpened is inserted in the slot 38 and pressed down to engage its edge in the grooved blocks 48 and 49. Thus the blade is held perfectly vertical under pressure of the jaws 40 and M. Said jaws compensate, by their yielding nature, for any differences in thickness between blades requiring sharpening. As the abrasive elements l6 act upon opposite faces of a blade the latter is gradually shifted lengthwise through the machine allowing the latter to act on the full length. If the blade has a curved portion the knife is tilted vertically to constantly maintain a downward pressure on the edge portion within the machine. The described machine not only quickly produces a very sharp edge, but assures that such edge will have a constant included angle throughout the blade length and will be accurately located in the medial plane of the blade. In case a blade edge is erratic with respect to the medial plane, the described machine will effecta proper correction of such edge. It may further be noted that the machine is small and compact and requires little operating power.

Mounting of the guide 8 to slide to and from the guide 6 permits of a compensation for wear of the abrasive elements, and further permits of application to a blade of a yielding and regulable pressure, these results of course additionally requiring the described means for effecting the sliding adjustment and for regulating pressure of the spring 25.

The abrasive elements may be of any known type and, if preferred, may have cutting edges.

What I claim is:

1. In a knife sharpening machine, the combination with a pair of spaced carriages, of a pair of guides mounting said carriages and providing paths converged at an acute angle for sliding travel of the carriages, abrasive elements carried by the carriages and substantially confronting a plane bisecting said angle, means for positioning a blade to be sharpened substantially in said bisecting plane for engagement by the abrasive elements, means for reciprocating the carriages in said converged paths, means for guiding one of said guides in a sliding travel to and from the companion guide, and means for adjusting the sliding guide toward the companion guide, including a provision for yieldably urging the sliding guide toward the companion uide.

2. In a knife sharpenin machine, a casing having a pair of spaced parallel walls, a pair of spaced carriages, a pair of guides for said carriages fitted between said walls and providing carriage paths converged at an acute angle, abrasive elements carried by the carriages and substantially confronting a plane bisecting said angle, means jointly mounted on said walls for positioning a blade to be sharpened substantially in said bisecting plane, for engagement by the abrasive elements, means for reciprocating the carriages in said converged paths, and means on at least one of said walls for guiding one of said carriages in a sliding travel to and from the companion carriage.

3. In a knife sharpening machine as set forth in claim 2, said blade-positioning means being free to float transversely to said bisecting plane, means on at least one of said Walls for guiding said positioning means in such floating movement.

4. A blade-p0sitioning means comprising a member having spaced parallel walls and a connecting wall, a slot being extended across said connecting wall and sufliciently intosaid parallel paths converged at an acute angle ior' sliding travel of the carriages, abrasive elements cari'ied bythe carriages and substantially confronting a plane bisecting said angle, means for positioning a blade to be sharpened substantially-:in said bi secting plane for engagement by the abrasive elements, means for reciprocating the carriages in said converged paths, means for guiding one of said guidesin a sliding travel-to-and from the companion guide, an adjusting screw ioractuating the sliding guide toward the companion guide,

and a spring transmitting thrust from said screw to the slidingguide.

6. In a knife sharpening machine, the combination with a pair of spaced carriages,=of-a pair of guides mounting said carriages and providing paths-converged at an acute angle for sliding travel of the carriages, abrasive elements carried by the carriages and substantially confronting-a plane bisecting said angle; means for positioning ablade to be sharpened substantially in said bisecting plane for engagement by theabrasive elements, means for reciprocating the carriages in said converged paths, means for guiding one of said guides in a sliding travel to and from the companion guide, a spring urging the sliding guide toward the companion guide, and means for regulating the stress of said spring.

'7. In a knife sharpening machine, the combination with a pair of spaced carriages, of a pair of guides mounting said carriages and providing paths converged at an acute angle for sliding travel of the carriages, abrasive elements carried by the carriages and substantially confronting a plane bisecting said angle, there being at least two such elements on each carriage, with a material space therebetween, means for positioning a blade to be sharpened substantially in said bisecting plane for engagement by the abrasive elements, such positioning means at least partially occupying said space, and means for reciprocating the carriages in said converged paths.

8. In a knife sharpening machine, the combination with a carriage, means for guiding said carriage in a reciprocating travel, means for actuating the carriage in such travel, positioning means for a blade to be sharpened, and a pair of abrasive elements mounted on the carriage to engage a blade positioned by said positioning means and spaced apart to at least partially accommodate the positioning means between said elements.

9. In a knife sharpening machine, the combination with a pair of spaced carriages, of a pair of guides mounting said carriages and providing paths converged at an acute angle for sliding travel of the carriages, abrasive elements carried by the carriages and substantially confronting a plane bisecting said angle, means for positioning a blade to be sharpened substantially in said bisecting plane for engagement by the abrasive elements, a pair of intermeshed gears, means for driving one of said gears, and connecting rods extending from the respective gears to the respective carriages, and imparting reverse reciprocation to the carriages. 10. In a knife sharpening machine, a casing having a pair of spaced parallel walls, a pair of.

spaced carriages, a pair of guides ..for said car riages: fittedubetween said walls and providing. carriage paths converged at an acute angle, abrasive elements carried by the carriages and substantially confronting a plane bisecting said angle, a unit. fitted between said walls and dispo's'edrbetween-jsaidsguides for positioning a blade for engagement by'ithe abrasive elements, means oILat leastone of said walls for guiding said unit in'a floating travel to and from said carriage, guidesizincludingian actuating element exterior torit-hecasing for adjusting one of said guides to and from. the other guide.

:11. Ina knife sharpening machine, the combination with'za/riair. ofLspaced carriages, of a pair of guides mounting said carriages and providing carriage paths converged at an acute angle, abrasive= elements .carriede. by the. car'r'iagesa'and substantially confronting: a'zplan'e bisectingarsaid angle; means sfor reciprocating theicarriages in said converged pathsyan'd aunit disposedbetweexi saidr-guides fontpositioning a-rblade to" be sharp; ened: said unit; comprising a pairio'f walls rspiaiced, tozvaccommodate said .abrasivefrelements; "and means between said walls -forengagings'opposite sides of a blade; is

12. A'knife sharpening machine'as set: forth in claim 11',- thespaced walls ofsa'idsunit. being slottedrto-accommodate:saidblade'; *7

13. A knife sharpening machine as set forth in claim 11, the blade-engaging means of said unit being substantially equidistant from said walls of the unit.

14. In a knife sharpening machine as set forth in claim 11, means on said walls of the unit for seating the edge portion of a blade.

15. In a knife sharpening machine, the combination with a pair of positioning members spaced to receive a blade therebetween and means for yieldably thrusting said members toward each other to engage a blade, of two pairs of abrasive elements, said pairs being positioned for respectively engaging the respective sides of a blade between said positioning members, the abrasive members of each pair being spaced to accommodate therebetween at least one of said positioning members, and means for reciprocating said abrasive elements transversely to the length of a blade positioned by said positioning members.

16. In a knife sharpening machine, the combination with a pair of spaced carriages, of a pair of guides mounting said carriages and providing paths converged at an acute angle for sliding travel of the carriages, abrasive elements carried by the carriages for oppositely engaging a knife positioned between said elements, means for reciprocating the carriages insaid converged paths, means for guiding one of said guides in a sliding travel to and from the companion guide, and means for adjusting the sliding guide toward the u companion guide, including a provision for yield- 7 means for guiding one of said guides in a slidin travel to and from the companion guide, an adjusting screw for actuating the sliding guide toward the companion guide, and a spring transmitting thrust from said screw to the sliding guide.

18. In a knife sharpening machine, the combination with a pair of spaced carriages, of a pair of guides mounting said carriages and providing paths converged at an acute angle for sliding travel 01" the carriages, abrasive elements carried by the carriages for oppositely engaging a knife positioned between said elements, means for reciprocating the carriages in said converged paths, means for guiding one of said guides in a sliding travel to and from the companion guide, a spring urging the sliding guide toward the companion guide, and means for regulating the stress of said spring.

19. In a knife sharpening machine, the combination with a pair of spaced carriages, of a pair of guides mounting said carriages and providing paths converged at an acute angle for sliding travel of the carriages, abrasive elements carried by the carriages, for oppositely engaging a knife positioned between said elements, a pair of intermeshecl gears, means for driving one of said gears, and connecting rods extending from the respective gears to the respective carriages and imparting reverse reciprocation to the carriages 20. In a knife sharpening machine, the combination with a casing and a pair of carriages rela- 8 i tively spaced within the casing, of a pair of guides for the carriages mounted on opposed walls of the casing and providing paths converged at an acute angle for sliding travel of the carriages, means for reciprocating the carriages in said paths, abrasive elements respectively carried by the respective carriages for oppositely engaging a knife positioned between said elements, a screw mounted in one wall of the casing and having an actuating portion exterior to the casing, means operable by said screw for adjusting one of the carriages toward the other to compensate for abrasive wear, and indexing means for said screw exteriorly carried by the casing.

GLEN M. CALVERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 447,700 Schulze-Berge Mar. 3, 1891 531,368 Fifield Dec. 25, 1894 1,376,634 Penny May 3, 1921 1,444,374 Ensign Feb. 6, 1923 1,925,108 Nagy Sept. 5, 1933 2,024,860 Hobart Dec, 17, 1935 2,142,165 Blankner Jan. 3, 1939 2,228,385 Burns Jan. 14, 1941 

